Drier-Than-Normal Year Forecast In Missouri Basin
The Corps of Engineers’ forecast continues to call for below-average runoff in the Missouri River basin.
“The runoff in February was less than predicted, and we expect the lower-than-average runoff to continue in the coming months,” said John Remus, chief of the Corps’ Missouri River Basin Water Management Division.
“The snow accumulation in both the plains and the mountains continues to be below average, and the soil moisture remains very low compared to normal,” Remus said. “This resulted in us lowering our anticipated runoff for the 2022 water year.”
The 2022 calendar year runoff forecast above Sioux City, Iowa, has dropped from 21.7 million acre feet (maf.) last month to 20.4 maf. on March 1, a reduction of 1.3 maf. If realized, this forecast would be 79 percent of normal.
Runoff forecasts incorporate several factors including end-of-February soil moisture conditions, plains snowpack, mountain snowpack and long-term precipitation and temperature outlooks. Based on these factors, runoff is expected to be well below normal for all reaches except from Gavins Point Dam to Sioux City.
February runoff in the Missouri River Basin above Sioux City was 0.9 maf., 78 percent of average. Runoff was below average due to lack of snow accumulation coupled with the drier-than-normal soil conditions in the upper basin. Drought conditions are about the same as they were at the beginning of February, with 89 percent of the basin experiencing abnormally dry or drought conditions.
System storage is currently 48.1 maf., 8.0 maf. below the base of the annual flood control zone. The system will continue to serve all congressionally authorized purposes during 2022, including flood control, navigation and water supply, the Corps said.
Navigation flow support for the Missouri River is expected to be at minimum levels for the first half of the 2022 season, which begins April 1 at the mouth of the river near St. Louis, Mo. Flow support for the second half of the navigation season, as well as navigation season length, will be based on the storage in the system on July 1.
Mountain snowpack in the upper Missouri River Basin is accumulating at below-average rates. The February 27 mountain snowpack in the Fort Peck reach was 80 percent of average, while the mountain snowpack in the Fort Peck to Garrison reach was 82 percent of average. By March 1, about 80 percent of the total mountain snowpack has typically accumulated. Mountain snowpack normally peaks near April 15.
Currently, plains snowpack in the upper Missouri River Basin is very light to non-existent, the Corps said.
The six mainstem hydropower plants generated 448 million kWh of electricity in February. Typical energy generation for February is 624 million kWh. The power plants are expected to generate 7.4 billion kWh this year, compared to the long-term average of 9.4 billion kWh.
